Method of making gaseous glow tubes



y 1960 s. KUCHINSKY ETAL 2,946,642

METHOD OF MAKING GASEOUS GLOW TUBES Filed Feb. 13, 1959 OTHER SET OF ASSEMBLE SEAL CATHODES TU BE GLOWS REVERSE g I I PROCESS l BAKE corm ECT ALL CATHODES U AND CATHO DES GLOW EXHAUST m TWO SETS SEPARATELY F|LL WITH gi ig g' GAS GLOWS mmvrm l I SAUL AUCH/NS/(V BY THOMAS D. PH'EESON ATTORNEY United States Patent 2,946,642 METHOD OF MAKING GASEOUS GLOW TUBES Filed Feb. 13, 1959, Ser. No. 793,189

11 Claims. (Cl. 316-26) This invention relates to gaseous. indicator glow tubes and particularly to improved methods of preparing such tubes.

Gaseous glow tubes of the type contemplated by the present invention generally comprise a transparent envelope which contains an anode electrode, a plurality of cathode glow electrodes and a gas suitable forsupporting cathode glow. When a suitable electrical potential is applied between the anode and a cathode electrode, the cathode glows, that is, a sheath of gas surrounding the cathode glows and space current flows through the gas from the cathode to the anode. The cathodes generally include a main body portion in the form of a numeral, letter, or the like, and a lead wire which is connected to one of the tube pins or prongs within the tube envelope. Since each cathode and its lead is, in effect, one continuous electrode, if the lead and its pins are not coated with an insulating material, these parts may glow when the main body of the cathode glows. Since, for many reasons, it is desirable to use uncoated lead wires and pins, a problem arises concerning the selective processing of the cathodes and their leads and pins to insure that only the. main body of each cathode glows and not the leads and pins.

Accordingly, the objects of the present invention concern the provision of improved gaseous glow tubes and an improved method of making the same. r

In brief, a method of preparing a gaseous indicator glow tube, according to the invention, relates particularly to the aging process and is employed after cathode and anode electrodes are mounted in an envelope which is evacuated and filled with a suitable gas under pressure. The aging process of the invention is particularly eifective in a tube in which the anode is a comparatively large-area electrode and in which a shield means is provided between the main body portions of the indicator glow cathodes and the leads and pinsconnected thereto. In the first step of the aging process of the invention, with the anode and shield means maintained electrically neutral, the cathode electrodes are electrically connected in two groups. An alternating voltage is applied between the two groups of cathodeelectrodes so that, first, one group is caused to glow and, then, the other group is caused to glow. The next step comprises cyclically turning on each of the cathodes in order for a short time with operating voltages applied between the cathodes and the anode. Under some circumstances, it may also be desirable to include a reverse processing step in which the anode is operated as a cathode and glows 'andjthe cathode is operated as an anode and does not glow. These processing steps appear to selectively process the cathode electrodes so that, in normal operation of the tube, only the main indicator portions of the cathodes glow and not the cathode leads and pins. The efiicacy of the invention is not limited to grouping of the cathode electrodes in two sets during the aging process. More than two tively.

groups may be also be employed eifec- 2 I The invention is described in greater detail by reference to the single sheet of drawings wherein:

Fig. l'is a perspective view, partly in section, of a gaseous indicator tube prepared according to the method of the invention; and I a Fig. 2 is a flow chart of the steps of the method of the invention.

Referring to the drawings, a typical gaseous indicator glow tube 10 according to the invention includes an envelope 12 which has been evacuated and filled with a gas such as neon or the like at a suitable pressure to sustain cathode glow. The pressure may be about 50 to mm. of Hg. The envelope includes a base, or stem 14, through which metal pins or prongs 16 extend and by means of which electrical connection is made to suitable external electrical circuit elements. Two diametrically opposed pins 16 are adapted to receive and support the various electrodes of the .tube and are provided with a suitable insulating coating (not shown). The envelope 12 also includes a transparent viewing window 20 through which glowing indicator cathode electrodes 22' are viewed. A sealed off exhaust tubulation (not shown) is provided in the stem 14.

The indicator cathode electrodes 22 of may take substantially any desired shape; :for example, they may be numbers, letters, or the like, and they may be as few in number as desired, or there may be as many as is practical for the size of the. tube. Such cathodes are comparatively fragile and have small surface areas. In one form of the tube 10 wherein the cathode elements are numbers, ten of such elements are provided, including the numbers 0 to 9. Fewer than ten cathodes are shown in Fig. 1 for purposes of simplification of the drawing. The cathode elements 22 are made of any suitable metal, for example, stainless steel, aluminum, Ni-' vertical axis of the tube and facing the viewing window:

20 of the envelope 12. The cathode elements 22 are mounted with suitable insulating spacers 24 threaded on the posts 16' between them, the spacers being larger than the apertured tabs 23 and having suiilcient surface area to cover and insulate the tabs to assist in preventing them from glowing. The stack of electrodes islocked on the posts by mica rings 26, or the like.

Each cathode indicator element is'provided with a fine wire connecting lead 28 which may be integral with the apertured tab 23 or it may be secured thereto in any suitable manner. Each lead 28 is welded or otherwise secured at its free end to one of the pins 16 within the A pair of diametrically opposedlongitudinal slots 36.

and 38 are provided in the wallet the cup adjacent to and aligned with the support posts 16'. The base of the cup 30 rests on, but is insulated from, the pins 16 by an insulating disk 40 of mica or the like The anode cup is also electrically connected to one of the pins 16 y a suitable lead 42 which passes through an aperture '44 in its base 32. i

the at; 10

The cathode lead wires 28 extend from the cathodes through the slots 36 and 38 to the pins 16. The stack of cathodes is thus, in effect, contained within the cup. It is desirable, but not necessary, that the cathodes and their tabs and leads be arranged so that the leads 28 of adjacent cathodes pass through opposite slots to the proper pins. Thus, for example, the lead of the first cathode in the stack is attached to that portion of the cathode which is adjacent to slot 36, and the lead extends through slot 36 to its pin 16. The lead 28 of the next cathode in the stack is attached to that portion of the cathode which is adjacent to the slot 38 and extends through the slot 38 to its pin, and so forth, throughout" the stack.

In addition, considering all of the leads which pass through the slot 36, it is desirable, but not necessary, to pass the leads alternately to the right and to the left of the slot to the proper pins. Thus, the lead of the first cathode may pass to the right of the slot; the next may pass to the left of the slot, and so forth, through the stack. The above-described arrangement of the cathode leads provides optimum electrical and mechanical orientation of the leads to prevent shorts or the like.

It can be seen that the cup electrode 30 acts as a shield between the main body portion'of each cathode electrode 22 and its lead 28 and pin 16. With this arrangement, the anode cup assists in preventing the pins and leads from glowing when the cathodes glow.

A screen electrode 46 is mounted on the posts 16' at the top of the stack of cathode electrodes. The screen 46 is insulated from the adjacent cathode 22 by means of two of the spacers 24. The screen may be connected to the cup by metal tabs 48 so that it operates as part of the anode of the tube 10. The screen electrode also serves to trap metal sputtered by the cathode electrodes and thus prevents such metal from depositing on and clouding the viewing window.

According to the method of the invention, the tube 10 is prepared as follows referring to the flow chart of Fig. 2. First, the cathode indicator electrodes 22, the anode screen 46, and the cup electrode 30 are assembled on the tube stem 14, and the stem and envelope 12 are sealed together. The envelope and its contents are then baked and exhausted according to standard techniques and the envelope is filled with a suitable gas, such as neon, at a suitable pressure, in the range of about 50 to about 100 mm. Hg.

Next, the tube is aged. The aging of gas tubes, essentially, comprises operating the tube electrodes under rather drastic electrical conditions for a comparatively short time. The specific conditions employed in the aging process depend on several factors including tube size, gas pressure, and electrode sizes and materials. According to the invention, the following aging process was employed with a tube type 6844A having a height and diameter of about one inch, a gas pressure of about 70 mm. of Hg and stainless steel cathode electrodes of about .015 inch in width and about 0.65 inch in length.

In the first part of the process of the invention, the anode cup 30 is held electrically neutral and the cathode electrodes are connected in two groups. One group includes all cathodes having leads 28 which extend through the slot 36 in the cup 30, and the other group includes all cathodes having leads 28 which extend through the slot 38 in the cup 30.

The first step of the process comprises applying an alternating voltage between the two groups of cathodes so that first one group of cathodes glows and then the other group of cathodes glows. This operation is continued for about one hour with each group of cathodes being caused to glow separately for periods of about seconds. electrodes which are caused to glow, glow at greater than normal brightness, with the applied voltage being about 250 volts and the current per cathode being about four or five milliamperes.

The.

Next, each of the cathode numbers is caused to glow separately and more brightly than normal for about 48 hours with approximately 300 volts applied and about 4 milliamperes of current passed per cathode. The cathodes are turned on consecutively, and each is allowed to glow for a fraction of a second during this processing operation. After this operation has been performed, the cathode electrodes and the gas have been properly aged, and the tube itself is ready for operation.

Under some circumstances, for example, when aging tubes which utilize cathode electrodes of molybdenum or with tubes of other sizes, the method of the invention may be varied as follows. After the tube has been assembled and processed as above, up to the point of aging, the aging process is begun with a step which is called reverse processing. In this step, the anode cup is operated as the cathode, and the cathodes are operated collectively as the anode. The electrical parameters for this step comprise an applied voltage of about 300 volts and a total current flow of about 10 milliamperes. This step has a time duration of about 10 minutes, during which the cup electrode, operated as the cathode, glows brightly. Apparently impurities are removed from the gas and are trapped on the relatively large surface area of the cup. When this step is completed, the gas generally glows with its normal characteristic color which indicates that. a state of high purity has been achieved.

After the reverse aging step, the aging process described above is followed. If, during the aging process, the gas appears to assume a glow which is not its normal characteristic color, the above-described reverse processing operation may be employed again to recover the characteristic gas color.

It is clear that the principles of the invention do not require that, in the first step of the aging process, the cathodes be arranged in exactly two groups. More than two groups may also be used effectively. In addition, other gases than neon, for example, argon, krypton, or the like, may be used and the gas pressures may be varied within the scope of the invention. In addition, the time periods during which the cathode electrodes are operated and the aging currents and voltages may be varied, as will be appreciated by those skilled in the art. The essence of the method of the invention comprises aging the cathode electrodes in groups and with a shield provided between the main body portions of the cathodes and their leads and pins.

One advantage of the present invention resides in the fact that the aging process substantially eliminates the spurious glow of the tube pins and the lead wires which are connected to cathode electrodes. Thus, the pins and lead wires need not be coated with insulating material as has generally been required in the past. Another advantage of the method of the invention resides in the fact that the total aging time may be considerably reduced from that required with aging processes employed in the past.

What is claimed is:

1. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in two separate groups, first causing one group of cathodes to glow and then causing the other group of cathodes to glow, and then cyclically causing said cathodes to glow separately and consecutively.

2. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in two separate groups with adjacent cathodes being in different groups, first causing one group of cathodes to glow and then causing the other group of cathodes to glow, and then cyclically causing said cathodes to glow separately and consecutively.

4. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in two separate groups, holding said anode elec trically nuetral and applying an alternating voltage between said groups of cathodes so that first one group glows and then the other glows, and then cyclically causing said cathodes to glow separately and consecutively.

5. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in two separate groups with adjacent cathodes in difierent groups, applying an alternating voltage between said groups of cathodes so that first one group glows and then the other glows, and then cyclically causing said cathodes to glow separately and consecutively.

6. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, applying a voltage between said anode and all of said cathodes of such polarity that said anode is operated as a cathode and said cathodes are operated as an anode, electrically connecting said cathode electrodes in two separate groups, applying an alternating voltage between said groups of cathodes so that first one group glows and then the other glows, and then cyclically causing said cathodes to glow separately and consecutively.

7. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in separate groups, applying an alternating voltage between said groups of cathodes so that first one group glows and then another glows, and then cyclically causing said cathodes to glow separately and consecutively.

8. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, maintaining said anode electrically neutral, electrically connecting said cathode electrodes in separate groups, applying an alternating voltage between said groups of cathodes so that first one group glows and then another glows, and then cyclically causing said cathodes to glow separately and consecutively by applying operating voltage between each of them and said anode.

9. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode indicator electrodes having main body portions adapted to glow and each having a lead connected to a tube pin, the leads and pins being adapted not to glow, and an anode electrode providing a shield between said main body portions and the leads from said cathodes to tube pins, said method comprising, mounting said cathode and anode electrodes in said envelope with said anode effectively enclosing the main body portions of said cathodes and shielding them from the cathode leads, filling said envelope with a gas for promoting cathode glow, maintaining said anode electrically neutral, electrically connecting said cathode electrodes in separate groups, applying an alternating voltage between said groups of cathodes so that first one group glows and then the other glows, and then cyclically causing said cathodes to glow separately and consecutively by applying operating voltage between each of them and said anode.

10. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode electrodes adapted to glow and mounted within a cup-shaped anode electrode and having leads extending through slots in said anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in two separate groups, holding said anode electrode electrically neutral, first causing one group of cathodes to glow and then causing the other group of cathodes to glow, and then cyclically causing said cathodes to glow separately and consecutively by applying an operating voltage between each cathode and the anode.

11. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode electrodes each including a main body portion adapted to glow and a lead which does not glow and an anode electrode, said method comprising the steps of mounting said cathode and anode electrodes in said envelope with said anode shielding the main body of each cathode from its lead, filling said envelope with a gas for promoting cathode glow, electrically connecting said cathode electrodes in two separate groups, maintaining said anode electrically neutral, first causing one group of cathodes to glow and then causing the other group of cathodes to glow, and then cyclically causing said cathodes to glow separately and consecutively by applying operating voltage between each cathode and the anode.

References Cited in the file of this patent UNITED STATES PATENTS 2,401,040 Becker May 28, 1946 

